This invention is concerned with a method or process for converting synthesis gas, such as mixtures of gaseous carbon oxides with hydrogen or hydrogen donors to form hydrocarbon mixtures and oxygenates. The invention is concerned with an arrangement of processing steps for increasing the yields of high octane gasoline boiling components and light oil materials suitable for use as diesel fuel over that obtained heretofore in the known Fischer-Tropsch synthesis gas conversion process. In still another aspect, this invention is concerned with the use of a novel class of crystalline zeolites represented by ZSM-5 crystalline zeolite for improving the product distribution obtained from a Fischer-Tropsch synthesis gas conversion operation.
The world's largest oil from coal producing plant is known as the Sasol project in South Africa where petroleum products and chemicals are producted from high ash bituminous coal. The Sasol project works two variations of the Fischer-Tropsch synthesis gas conversion operation using a fixed and fluid catalyst bed system. This Sasol project has been described in British Chemical Engineering for the months May, June and July 1957. One portion of these articles of particular interest is concerned with the product recovery that is discussed in the July 1957 article.
The Sasol project referred to above and built to convert an abundant supply of coal to hydrocarbons, oxygenates and chemicals was a pioneering venture. The process complex developed is enormous by any standard and quite expensive to operate. Therefore any advances which can be made to improve the yield of desired products without significantly increasing operating expense is viewed as one of major importance. The processing concepts of this invention are considered to fall in that category.